The present invention relates to a manufacturing method for a red phosphor composed of europium-activated yttrium oxide (to be called hereinafter "Y.sub.2 O.sub.3 : Eu"), and particularly to a manufacturing method for a Y.sub.2 O.sub.3 : Eu red phosphor in which a composite flux composed of Na.sub.2 Co.sub.3, NaF and B.sub.2 O.sub.3 is used in manufacturing the phosphor so that the distribution of the partical size should become uniform, the shape of the particles should become spherical, and the luminesence should be improved.
Conventionally, when manufacturing a Y.sub.2 O.sub.3 : Eu phosphor for use in a projection tube, a composite flux/composed of Na.sub.2 CO.sub.3, K.sub.2 HPO.sub.4 and B.sub.2 O.sub.3, or H.sub.3 BO.sub.3, NaF and Na.sub.2 CO.sub.3 was used.
However, the conventional phosphor manufactured based on the above described method was not uniform in its particle shapes, with the result that the manufactured phophor layer showed a lowered luminance.